HELP!!! (w/ short passage of rapid inversions)

[dlu]

I am currently working on Shostakovich's 2nd piano concerto. Um.... The concerto is incredibly straight forward except for one passage in the first movement which has 5 eigth note chords played at (quarter note)=132 (that is my chosen tempo for the first movement which is actually pretty slow compared to the other performances I have heard). Here are the chords which are the same in the right hand and left (the right hand of course is 8va above the left):
a-c-f/c-f-a/f-a-c (the next two chords are the same as the first two chords i.e. going down...not up the keyboard like the first three chords) c-f-a/a-c-f

I don't see why I am having trouble with these simple 5 inversions. What fingerings would you suggest or just anything that might make this a little easier. Yes, I have tried them very slowly then "uped" the metronome to my goal (132) but i screw up when it gets closer to 132 and i can play the entire first movement at 132 except for those stupid chords. My right hand does it O.K. but the left seems to drop out fter the 2nd or third chord. And no I will not decrease my set tempo  of 132.
If you really need to see the notation of the chords to help me i could mabye post a picture but only if you really need to see them because my scanner has been f****** up lately and I don't want to break it (it doesn't actually belong to me).
Thanks for you posts in advance,
DLu